1. Field of the Invention
The present invention relates to a dental system for the transillumination of teeth. The dental system has a light source for producing examination radiation, irradiation means for directing the examination radiation at a tooth to be examined, and means for acquiring an optical image of the tooth illuminated by the examination radiation.
2. Related Technology
In medicine, in particular in dentistry, diagnostic systems based on optical principles are increasingly being used. The reason for this is that such devices usually allow a diagnosis to be made without contact, that is to say in particular in a pain-free manner, and, in addition, often also provide optical images with which any necessary therapeutic measures can be communicated to the patient graphically and hence more clearly. For example, so-called intraoral cameras are used in dentistry, which cameras include a handpiece, the front end region of which is introduced into the mouth of a patient. In that end region there is generally a light-entry or viewing window for the camera lens, from which the image of the object to be examined is transmitted to an acquisition device, for example a CCD chip.
Such an intraoral camera can further be extended to a system for the transillumination of teeth, as is known inter alia from DE 10 2006 041 020 A1 of the applicant. In that system, the tooth to be examined is irradiated with light within a specific wavelength range, an optical image of the tooth illuminated by the examination radiation then being acquired and evaluated. Because carious areas in the tooth scatter the light differently than healthy dental tissue, such areas can be identified when the tooth is observed with the aid of a camera, it even being possible, if the system is suitably configured, to obtain a more reliable caries diagnosis than is the case with a conventional X-ray examination.
The quality of the images produced in this procedure, and hence ultimately of the caries diagnosis, is dependent to a critical extent on the way in which the light is coupled into the tooth to be illuminated. In DE 10 2006 041 020 A1 there is used for that purpose a special head-piece of an instrument, which rests on the tooth. If excessive irradiation occurs as a result of illumination of the light sensor directly or by reflection, a computational elimination of those image regions is carried out. However, this has the disadvantage that the dynamic range of the system is limited on account of the computational possibilities.
As an alternative thereto there is known from U.S. Pat. No. 4,184,175 a polarizing filter for removing reflected light or direct light. However, the polarization causes a loss in intensity in the illumination of the tooth, which represents a not inconsiderable disadvantage. Finally, U.S. Pat. No. 6,672,868 describes a device which has mechanical means for blocking light, by which the direct ingress of reflected light or direct light in the light sensor is reduced. However, such measures result in an enlarged construction of the front end region of the device, which is a disadvantage because of the already restricted room for maneuver inside the oral cavity of the patient.